The invention relates to a method for determining a required shape for at least one surface of an artificial or natural part of the eye which is intersected by a path of rays through the pupil of the eye. The invention also relates to a device for the manufacture of an artificial lens.
The cornea and lens are natural parts of an eye which are intersected by a path of rays passing through the pupil of an eye. In addition to this however, optical fittings can be placed or surgically attached to the surface of the cornea, implants can be inserted into the inner cornea to vary the shape of the cornea, and further fittings can be placed into the anterior section or into the internal part of the eye to refract the path of rays passing through the eye.
The shape of the intersected surfaces is of great importance because the refraction power of the eye is altered by changing the shape of a surface that is intersected by the path of rays. The success of measures for the treatment of natural parts or artificially inserted or attached parts of the eye should be accurately determinable beforehand.
Major problems exist in predicting the success actually achieved, in particular for the coordination of several measures which alter the refraction power of the eye.
It is for example already known when manufacturing an artificial lens, to scan the curvature of the cornea of the eye at 4 points using keratometry, and to determine the approximate curvature of the total cornea surface area using extrapolation. In addition the distances between the anterior surface of the cornea, lens and retina are scanned using biometry to determine the curvature and refraction power of the lens respectively by means of the average curvature of the cornea in such a way that rays which are incident to the cornea, intersect at one point on the retina.
This method is suitable for a cornea with a very uniform curvature. In certain areas of the cornea, incident rays are in practice not focused at the attainable point because the curvature of the cornea, however, is as a rule different over the total area.
In addition, this method is only suitable for determining the surface of an artificial lens.